<template>
<div>
  <el-button @click="add">+ </el-button>
</div>
</template>
<script>
export default{
  data(){
    return{
      arr : [
      {a:1},
      ],
    }
  },
  methods:{
    add(){
      let obj = JSON.parse(JSON.stringify({
      a: this.arr[length].a + 1,
    }))
    this.arr.push(obj)
    console.log(this.arr);
    console.log(this.arr.length);
    }
  }
}
</script>
<style scoped>

</style>
    